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The formula for the contact potential of a pn-junction diode is given by the formula: (NaNa n? Aøo kT In a) This contact potential ensures that the net current across the junction is zero. Which side is higher in electron potential energy - the n or the p-side? Briefly explain your answer. b) Even though there is no net current across the pn-junction in equilibrium with no applied voltage (V=0), there are two individual currents associated with electrons that add to zero (and two more associated with holes) – drift and diffusion current. Explain what they are (and how they arise), and give their direction (for electrons). c) Which of the two types of current is independent of A$o? Briefly explain why.

The formula for the contact potential of a pn-junction diode is given by the formula: (NaNa n? Aøo kT In a) This contact potential ensures that the net current across the junction is zero. Which side is higher in electron potential energy - the n or the p-side? Briefly explain your answer. b) Even though there is no net current across the pn-junction in equilibrium with no applied voltage (V=0), there are two individual currents associated with electrons that add to zero (and two more associated with holes) – drift and diffusion current. Explain what they are (and how they arise), and give their direction (for electrons). c) Which of the two types of current is independent of A$o? Briefly explain why.

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The formula for the contact potential of a pn-junction diode is given by the formula: KT In (NaNa a) This contact potential ensures that the net current across the junction is zero. Which side is higher in electron potential energy – the n or the p-side? Briefly explain your answer. b) Even though there is no net current across the pn-junction in equilibrium with no applied voltage (V=0), there are two individual currents associated with electrons that add to zero (and two more associated with holes) – drift and diffusion current. Explain what they are (and how they arise), and give their direction (for electrons). c) Which of the two types of current is independent of A¢o? Briefly explain why. d) Arguing from the formula above for A$o, give a conceptual reason for the fact that germanium (Ge) diodes have about half the contact potential compared to silicon (Si) diodes, all else being equal (same doping concentrations and temperature). For a photodiode (PV cell), would you choose Si or Ge, and why?
Transcribed Image Text:The formula for the contact potential of a pn-junction diode is given by the formula: KT In (NaNa a) This contact potential ensures that the net current across the junction is zero. Which side is higher in electron potential energy – the n or the p-side? Briefly explain your answer. b) Even though there is no net current across the pn-junction in equilibrium with no applied voltage (V=0), there are two individual currents associated with electrons that add to zero (and two more associated with holes) – drift and diffusion current. Explain what they are (and how they arise), and give their direction (for electrons). c) Which of the two types of current is independent of A¢o? Briefly explain why. d) Arguing from the formula above for A$o, give a conceptual reason for the fact that germanium (Ge) diodes have about half the contact potential compared to silicon (Si) diodes, all else being equal (same doping concentrations and temperature). For a photodiode (PV cell), would you choose Si or Ge, and why?
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